1. Field of the Invention
The present invention relates to a solid state imaging device including a solid state imaging element mounted on a packaging substrate, a method for producing the same, a solid state imaging unit including a lens mirror cylinder unit attached to the solid state imaging device, a method for producing the same, and an imaging apparatus using the same.
2. Description of the Related Art
Conventionally, a solid state imaging element including CCDs is used in various types of imaging apparatuses such as digital cameras and video cameras. When used in these imaging apparatuses, the solid state imaging element is combined with a lens mirror cylinder unit including an optical lens for focusing light, representing an image, on the solid state imaging element.
FIG. 4 shows a manner of combining a solid state imaging element 100B and a lens mirror cylinder unit. An optical axis L of an optical lens 100A of the lens mirror cylinder unit, and an imaging plane center C of the solid state element 100B, need to be positionally aligned with each other. The positional alignment is performed by adjustment of the angle of view based on X, Y and θ axes. In addition, a plane perpendicular to the optical axis L of the optical lens 100A needs to be parallel to an imaging plane of the solid state imaging element 100B. This is performed by focusing adjustment based on Z axis and tilt adjustment based on a and b axes. The tilt adjustment is performed for preventing partial defocusing. (The adjustment for preventing partial defocusing will be referred to simply as the “partial defocusing adjustment.) The positional adjustment based on the above-mentioned six axes is precisely performed in the micrometer (μm) order.
Conventionally, the positional alignment and adjustment based on these axes is performed over a long period of time using an expensive positional adjustment apparatus. For example, the positional alignment of the optical lens 100A and the solid state imaging element 100B is performed as follows.
As shown in FIG. 5, a package 101 having the solid state imaging element 100B mounted thereon is fixed to a metal plate 102 formed of, for example, aluminum, with an adhesive or the like.
Then, a lens mirror cylinder unit 103 having the optical lens 100A built therein is placed at a fixed position. With respect to the lens mirror cylinder unit 103, the solid state imaging element 100B is moved along and about the axes together with the package 101 provided on the metal plate 102, in units of very fine distance and very fine angle. By such movement, the optical lens 100A and the solid state imaging element 100B are positioned to have an optimal positional relationship, by which an output signal from the solid state imaging element 100B is optimal. In this position, the lens mirror cylinder unit 103 and the metal plate 102 hold the solid state imaging element 100B on the package 101. Thus, the solid state imaging element 100B and the lens mirror cylinder unit 103 are integrally fixed with each other by tightening members, such as screws 104 or the like.
In order to simplify the above-described step of positional alignment of the lens mirror cylinder unit 103 and the solid state imaging element 100B, the following proposals have been conventionally made.
Japanese Laid-Open Utility Mode Publication No. 5-46046 directed to a “Solid State Imaging Device” proposes the following technique. A solid state imaging element is mounted on apart of a flat plate having a surface polished so as to have a smoothness (surface roughness) of a maximum of about 5 μm. A package for covering this solid state imaging element is fixed such that the flat plate is partially exposed. The exposed part of the flat plate acts as a reference plane, i.e., a plane to which the lens mirror cylinder unit is to be attached.
According to Japanese Laid-Open Publication No. 2000-125212 directed to an “Imaging Module”, a flat part of a ceramic plate is used both as a reference plane of a semiconductor chip and a reference plane of a lens mirror cylinder unit.
Japanese Laid-Open Publication No. 10-326886 directed to “Solid State Imaging Device and Method for Mounting Solid State Imaging Device” and Japanese Laid-Open Publication No. 2000-307092 directed to “Solid State Imaging Device, Camera Using the Same, and Method for Producing the Same” propose the following technique. A pilot portion which is opened outward is provided on a side surface of a package, and a guide portion which is opened outward is provided on a side surface facing the side surface provided with the pilot portion. Using the pilot portion and the guide portion, a solid state imaging element, a lens mirror cylinder unit and a wiring board are positioned with respect to each other by a jig having pins projecting therefrom.
The above-described conventional techniques have the following problems.
According to the techniques described in Japanese Laid-Open Utility Mode Publication No. 5-46046 and Japanese Laid-Open Publication No. 2000-125212, the plane vertical to the optical axis of the optical lens and the imaging plane of the solid state imaging element can be adjusted to be parallel to each other with high precision, for the following reason. Since the plane on which the solid state imaging element is mounted and the plane on which the lens mirror cylinder unit is mounted are coplanar, the adjustment based on Z axis (FIG. 5) (which is provided for focusing adjustment) and based on a and b axes (which are provided for tilt adjustment for partial defocusing adjustment) is performed with high precision. However, the optical axis of the lens mirror cylinder unit and the imaging plane center of the solid state imaging element cannot be aligned with high precision. The reason for this is because there is no reference position or plane for X, Y and θ axes, which are parallel to the plane on which the solid state imaging element is mounted.
According to the technique described in Japanese Laid-Open Publication No. 10-326886 and Japanese Laid-Open Publication No. 2000-307092, the positional alignment of the optical axis of the lens mirror cylinder unit and the imaging plane center of the solid state imaging element, i.e., the adjustment based on X, Y and θ axes, can be performed with high precision, by use of the pilot portion, the guide portion and the jig having pins projecting therefrom. However, the plane vertical to the optical axis of the optical lens and the imaging plane of the solid state imaging element cannot be adjusted to be parallel to each other with high precision. The reason for this is because there is no reference position or plane for Z axis (parallel to the pilot portion and the guide portion) provided for focusing adjustment and a and b axes provided for tilt adjustment for partial defocusing adjustment. Even for the positional adjustment based on X, Y and θ axes, this technique has inconveniences of requiring a positional adjustment jig having pins projecting therefrom and also requiring an additional step of alignment using the positional adjustment jig.